This invention relates to a ball bearing made of a synthetic resin material which can sufficiently bear not only a radial load but also a thrust load.
Conventionally as shown in FIG. 5, steel balls c are arranged in two rows between an inner race a made of a synthetic resin material having a bore a' and an outer race b also made of a synthetic resin material. The inner race a comprises a small diameter half a.sub.1 and a large diameter half a.sub.2 fitted each other. A plurality of steel balls c are nested in an annular groove G defined by side walls a.sub.3 and a.sub.4 of the respective halves a.sub.1 and a.sub.2 opposite each other. The balls c are arranged in two rows by an annular projection b.sub.1 formed in an intermediate portion of the inner surface of the outer race b. Both side surfaces b.sub.2 of the annular projection b.sub.1 are formed generally rounded so that they will be totally snugly contacted with the outer surfaces of the balls c.
However, with the above construction, since the dimension of the side wall portion b' of the outer race b is small compared with the inner race a mounted to the shaft through the bore a', the thrust load cannot be easily applied to the outer race portion of the synthetic resin bearing. Especially, when the bearing is made small, it is almost impossible to apply the thrust load thereto.
Similarly, with the above construction, the peripheral diameter of the surface of the ball is large. Therefore, since the wear of the rolling balls as well as the wearing amount of the surface of the passage on which the balls contact are large, the service life of the bearing is short. Moreover, since the space between the inner race and the outer race is positioned at the outer peripheral portion of the bearing as a while, the internal grease leaks out due to the centrifugal force. Moreover, since the demension of the opening portion is large, dust proof performance is poor.
The present invention has been accomplished in order to solve the above problems.